1. Field of the Invention
The present invention relates to a liquid image forming apparatus and a method thereof, and more particularly, to a liquid image forming apparatus which can reduce deformation of an image film formed on a photoreceptor web, and a method thereof.
2. Description of the Related Art
An image forming apparatus is divided into a liquid type and a dry type according to the type of developer used. The liquid image forming apparatus uses developer in which toner in a powder state is distributed in a volatile liquid carrier. In the liquid imaging system, an electrostatic latent image is formed by emitting a laser beam onto a photoreceptor web or organic photoreceptor (OPR) circulating along an endless path. Liquid toner is supplied to develop the electrostatic latent image into a toner image and the toner image is transferred to a printing paper.
FIG. 1 shows the structure of a conventional imaging system. Referring to FIG. 1, a photoreceptor web 110 is supported by a backup roller 111, a steering roller 112, and a driving roller 113. The backup roller 111 presses the photoreceptor web 110 to provide a predetermined pressure to the transfer roller 114 installed adjacent thereto to transfer a toner image in a film state formed on the photoreceptor web to the transfer roller 114. A press roller 115 in contact with the transfer roller 114 at a predetermined pressure is installed at one side of the transfer roller 114 to transfer the toner image adhering to the transfer roller 114 to a print paper 116 passing between the transfer roller 114 and the press roller 115.
An image forming apparatus 200 for forming the toner image on a surface of the photoreceptor web 110 is disposed along the photoreceptor web 110 between the steering roller 112 and the driving roller 113. The image forming apparatus 200 includes laser scanning units (LSU's) 202a, 202b, 202c, and 202d, using a laser beam and developing units 201a, 201b, 201c, and 201d, which are alternately installed. For each color, that is, yellow, magenta, cyan and black, a laser scanning unit and a developing unit adjacent thereto form a toner image unit.
The laser scanning units 202a, 202b, 202c, and 202d, emit a laser beam onto the surface of the photoreceptor web 110 according to an image signal per color to form an electrostatic latent image. The developing units 201a, 201b, 201c, and 201d, develops the latent image formed by the laser scanning units to a toner image.
The developing units 201a, 201b, 201c, and 201d, of the image forming apparatus 200 each include a developing roller for coating a developer of a predetermined color on the photoreceptor web 110, and a squeeze roller for removing excess developer coated on the photoreceptor web 110.
An image drying roller 120 for removing liquid carrier remaining on the toner image from the photoreceptor web 110 is provided to be adjacent to the driving roller 113. The surface of the image drying roller 120 consists of an outer surface having an affinity for oil for absorbing the liquid carrier from the photoreceptor web 110 and an inner surface disposed under the outer surface and having an anti-oil characteristic for preventing intrusion of the liquid carrier. The image drying roller 120 absorbs the liquid carrier remaining on the surface of the photoreceptor web 110 while being rotated in contact with the photoreceptor web 110. Two heating rollers 121 and 122 separated a predetermined distance from each other are in contact with the image drying roller 120. The heating rollers 121 and 122 heat the image drying roller 120 and vaporizes the liquid carrier absorbed in the surface thereof. The vaporized liquid carrier is collected by an additional collection apparatus (not shown).
In the conventional image forming apparatus 200 having the above structure, the image drying roller 120 performs a rolling movement while contacting the photoreceptor web 110. The image drying roller 120 should rotate adaptively corresponding to the movement of the photoreceptor web 110. If the image drying roller 120 rotates not complying with the movement of the photoreceptor web 110, the image drying roller 120 slips on the photoreceptor web 110. The slippage of the image drying roller 120 results in abrasion of the surface of the photoreceptor web 110, thus damaging the toner image on the photoreceptor web 110.
Damage to the toner image due to slippage of the image drying roller 120 occurs when the liquid carrier absorbed in the surface of the image drying roller 120 is accumulated over a predetermined degree. Particularly, when the image processing is performed for a long time and the amount of vaporization of the liquid carrier by the heating rollers 121 and 122 continuously exceeds that of the liquid carrier absorbed from the photoreceptor web 110, the image drying roller 120 slips on the photoreceptor web 110.
The slippage phenomenon also occurs when the image drying roller 120 continuously absorbs the liquid carrier while contacting the photoreceptor web 110 so that an appropriate temperature is not maintained during the continuous formation of an image. Such a phenomenon occurs at the conventional image forming apparatus so that a desired quality image cannot be obtained.